23.1 Fetal Complications: Malpresentation & Breech, Macrosomia, Fetal Growth Restriction, Amniotic Fluid Disorders, Antepartum Surveillance, Rh Alloimmunization, Multiple Gestation and Post-Term Pregnancy

Why this area matters

TOS area E covers:

• malpresentation, macrosomia and intrauterine growth restriction;
• risk factors and fetal conditions that lead to poor perinatal outcomes;
• maternal signs of fetal compromise;
• diagnostic tests and interventions;
• long-term consequences such as impaired brain development and chronic lung disease.

Low birth weight from preterm birth and growth restriction is common in the Philippines and is linked to maternal undernutrition, anemia, smoking, infection and adolescent pregnancy. Under the "first 1,000 days" approach (RA 11148, Kalusugan at Nutrisyon ng Mag-Nanay Act), maternal nutrition is part of preventing these problems.

Malpresentation and malposition

• External cephalic version (ECV) is offered for breech at 37 weeks or later if there is no contraindication. Contraindications include placenta previa, a reason for cesarean delivery anyway and ruptured membranes.
• Since the Term Breech Trial, planned cesarean is usual for a persistent breech. Vaginal breech delivery is reserved for selected frank or complete breeches with experienced attendants.
• Cord prolapse is an emergency. Lift the presenting part off the cord, place the mother knee-chest, keep the cord in the vagina and deliver by the fastest route.

Macrosomia

• Definition: birth weight above 4,000 g, or above 4,500 g by stricter definitions.
• Risk factors: maternal diabetes, obesity, excessive weight gain, post-term pregnancy and a previous macrosomic baby.
• Complications: shoulder dystocia and brachial plexus injury, clavicle fracture, perineal tears, cesarean delivery and postpartum hemorrhage. Newborns face hypoglycemia, and later obesity.
• Ultrasound weight estimates have large errors. Prophylactic cesarean may be offered when estimated weight is above 5,000 g without diabetes or above 4,500 g with diabetes.

Fetal growth restriction (FGR)

• Definition: estimated fetal weight or abdominal circumference below the 10th percentile.
  • Symmetric FGR starts early and affects the head and body equally. Causes are aneuploidy, congenital infection (TORCH), and drugs or alcohol.
  • Asymmetric FGR starts later. The head is spared and the abdomen is small because of placental insufficiency, from preeclampsia, chronic hypertension, smoking, malnutrition, renal disease or antiphospholipid syndrome.
• Surveillance:
  • serial growth scans;
  • amniotic fluid;
  • umbilical artery Doppler: increased resistance, then absent and finally reversed end-diastolic flow;
  • middle cerebral artery Doppler, where "brain sparing" shows as low resistance;
  • ductus venosus Doppler and the biophysical profile.
• Timing of delivery balances prematurity against intrauterine risk:
  • normal Doppler: about 38 to 39 weeks;
  • absent end-diastolic flow: about 33 to 34 weeks;
  • reversed end-diastolic flow: about 30 to 32 weeks;
  • give antenatal steroids and magnesium as appropriate.
• Long-term effects: neonatal hypoglycemia, polycythemia and hypothermia; neurodevelopmental delay. Preterm survivors are at risk of chronic lung disease (bronchopulmonary dysplasia). In adult life there is a higher risk of hypertension, diabetes and cardiovascular disease (the developmental origins, or Barker, hypothesis).

Amniotic fluid disorders

• Oligohydramnios: single deepest pocket below 2 cm or AFI of 5 cm or less.
  • Causes: rupture of membranes, placental insufficiency, renal agenesis or urinary obstruction (Potter sequence: pulmonary hypoplasia, limb deformities), post-term pregnancy and ACE inhibitors.
• Polyhydramnios: single deepest pocket of 8 cm or more or AFI of 24 to 25 cm or more.
  • Causes: maternal diabetes, fetal swallowing defects (esophageal or duodenal atresia, anencephaly), twin-twin transfusion, fetal anemia and hydrops.
  • Risks: preterm labor, malpresentation, cord prolapse, abruption at membrane rupture and atony.

Antepartum fetal surveillance

• Fetal movement counting: reduced movement needs prompt evaluation.
• Nonstress test (NST):
  • reactive if there are 2 accelerations in 20 minutes, each of 15 bpm or more lasting 15 seconds or more after 32 weeks (10 bpm for 10 seconds before 32 weeks);
  • a nonreactive test leads to further testing.
• Biophysical profile (BPP): NST, fetal breathing movements, gross body movements, tone and amniotic fluid volume, each scored 2 or 0.
  • 8 to 10 is reassuring;
  • 6 is equivocal;
  • 4 or less calls for delivery in most cases.
• A contraction stress test looks for late decelerations with contractions.

Rh (D) alloimmunization

• Mechanism: an Rh-negative mother exposed to Rh-positive fetal red cells forms anti-D IgG. In later pregnancies this crosses the placenta and causes hemolytic disease of the fetus and newborn, from anemia to hydrops fetalis and kernicterus.
• Prevention: anti-D immune globulin 300 mcg at 28 weeks and within 72 hours of birth of an Rh-positive infant, and after miscarriage, ectopic pregnancy, procedures, bleeding or abdominal trauma. The Kleihauer-Betke test measures fetomaternal hemorrhage to decide whether extra doses are needed.
• Sensitized pregnancy:
  • follow antibody titers;
  • once the critical titer is reached, use middle cerebral artery peak systolic velocity Doppler; above 1.5 multiples of the median suggests moderate to severe anemia;
  • treat by intrauterine transfusion or delivery.
• Rh-negative blood types are uncommon among Filipinos, so anti-D must be planned for in advance.

Multiple gestation and post-term pregnancy

• Twins:
  • Dizygotic twins are always dichorionic-diamniotic.
  • Monozygotic twins have chorionicity set by the timing of splitting:
    • before day 4: dichorionic-diamniotic;
    • days 4 to 8: monochorionic-diamniotic;
    • days 8 to 12: monochorionic-monoamniotic;
    • after day 12: conjoined.
  • Chorionicity is best determined in the first trimester (lambda sign versus T sign).
  • Monochorionic twins risk twin-twin transfusion syndrome, with a polyhydramnios recipient and an oligohydramnios donor, treated by laser ablation. Monoamniotic twins risk cord entanglement.
  • Twins in general risk preterm birth, preeclampsia, anemia and PPH.
• Post-term pregnancy (42 weeks or more): risks include oligohydramnios, meconium aspiration, macrosomia, postmaturity syndrome and stillbirth. Induction at 41 weeks reduces perinatal death.